The present invention is directed to multi-way calling, and more particularly to a bandwidth efficient method and apparatus capable of handling multiple simultaneous callers in a wireless communication system.
Typical three-way calling having at least one mobile wireless subscriber is either typically bandwidth inefficient or poor in voice quality or both. Such inefficiencies can be illustrated in a digital communication system where a three-way call needs to be set up between a mobile user xe2x80x9cMxe2x80x9d and two other users xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d. Users xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d can either be mobile units, PSTN users or Voice-over-Internet Protocol (VoIP) users. Focusing on M""s wireless connection to a base station, a three-way call can be set-up simply by allocating two downlink channels (one for xe2x80x9cAxe2x80x9d and one for xe2x80x9cBxe2x80x9d) and allocating one uplink channel for the mobile user xe2x80x9cMxe2x80x9d. The disadvantage of this approach is that it requires 1.5 times the bandwidth as a normal two-way conversation.
An alternative to the example above is to convert signals xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d back into analog voice waveforms, add the waveforms, and then re-code the composite waveform into a single downlink channel. This solves the bandwidth efficiency problem of the method above, but it adds additional complexity to the system in terms of the decoding and then re-coding of the voice information. Furthermore, Very Low Bit-rate (VLB) vocoders do not perform well when the input waveform consists of more than one voice. Therefore, combining the two voices from xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d followed by re-coding of the signal would degrade the call quality.
Thus a need exists for a bandwidth efficient method and apparatus that would allow for multi-party calls, preferably using a VLB adjustable vocoder with minimal impact on voice quality.